Health conditions can be found through analysis of the composition or the concentration of gases contained in the breath.
For example, the acetone produced in the conversion of the accumulated free fatty acids in the body into blood glucose discharges out of the body with the breath. If the body fat combustion rate could be estimated from the concentration or the discharge amount of acetone, it would be possible to use the information for health management such as dieting.
The detection accuracy of a semiconductor gas sensor is not sufficient for the measurement of the concentration or the discharge amount of trace amounts of acetone in the breath, and a gas chromatography mass spectrometer is too large for this purpose.